1. Field of the Invention
This invention relates to an indirect-plunger hydraulic elevator, in particular to an indirect-plunger hydraulic elevator that is moved up and down through a wire rope driven by a hydraulic jack.
2. Description of the Related Art
A conventional indirect-plunger hydraulic elevator is shown in FIGS. 7 through 10. In FIG. 7, symbol 1 shows an elevator car comprising a box-type car enclosure 2 and a car frame 3 supporting the car enclosure 2. The car frame 3 comprises a top beam (crosshead) 4, a couple of vertical frames (slings) 5 hanging downwardly on the right-hand side end and the left-side end respectively of the top beam 4, a bottom beam 6 fixed between each lower end of the vertical frames 5, and a car platform supporting frame 7 fixed on the bottom beam 6. On the car platform supporting frame 7, the car enclosure 2 is set through a vibration-preventing rubber 8.
As shown in FIGS. 8 and 9, the bottom beam 6 of the car frame 3 consists of a couple of long-sized channel-shaped frames enclosing the lower end portions of the vertical frames 5. On the lower side of the bottom beam 6, a safety device 9 is attached. In case of emergency, the safety devices 9 contact with guide rails 10 which are set to the right hand side and the left hand side of the bottom beam, respectively, to stop the car immediately.
Furthermore, on the lower side of the bottom beam 6 is a sheave supporting beam 11. This sheave supporting beam 11 consists of a couple of channel-shaped frames and is fixed to the lower side of the bottom beam by welding, bolts or the like. At both ends of the sheave supporting beam 11, sheaves 12 are rotatably attached. The sheave supporting beam 11 is fixed diagonally in an adequate angle against the bottom beam 6 and it crosses the bottom beam 6 so as not to interfere with the safety devices 9 and guide rails 10 set at the right hand side and the left hand side of the bottom beam respectively.
On the right and left sheaves 12 attached at the lower portion of the car 1, an up and down driving wire rope 13 is winded or disposed and one end portion thereof is fixed to a beam 14 located at the upper end of a hoistway. Another end portion of the up and down driving wire rope 13 is connected to a jack stand 18 through sheaves 17 attached to an upper end portion of a plunger 16 of a hydraulic jack 15 set inside the hoistway. Therefore, this conventional indirect-plunger hydraulic elevator has 2 to 4 roping. The plunger 16 of the hydraulic jack 15 moves up and down so that the elevator car 1 moves up and down through the wire rope 13 at double the speed of the plunger 16.
The above mentioned conventional indirect-plunger hydraulic elevator has the bottom beam 6, which supports the car platform supporting frame 7 and the safety device 9, on the lower side of the car frame 3 of the elevator car 1. The hydraulic elevator also has the sheave supporting beam 11, which supports a pair of sheaves 12, on the lower side of the bottom beam 6. Those beams 6 and 11 are both similar long-sided channel-shaped beams and are set together one on top of the other as a double stage structure. Therefore, the structure of the lower side of the car platform becomes complex so that the construction of those beams 6 and 11 and the elevator car necessarily gains weight. Furthermore, because of setting the sheave supporting beam 11 and the bottom beam 6 one on top of the other the height (H) between the bottom of the car enclosure 2 to the bottom end of the sheaves 12 becomes large so that it is necessary to dig a pit deeply at the bottom end of the hoistway.